This disclosure relates to prefabricated ceramic crowns supported on dental implants.
One shortcoming of conventional dental implant restorations is that metal abutments can disrupt the translucence of the porcelain used to fabricate the crown. Dental abutments are typically made from titanium or other biocompatible metals. These metals are most often metallic gray in color and hence can have aesthetic disadvantages in dental restorations. In some instances, the abutment can be visible through the gingival tissue and present a grayish color in the transgingival region of the patient. Visibility of the abutment is greatly undesired, especially in the anterior region of the mouth where aesthetics have a crucial importance. In other instances, the tissue and bone surrounding the coronal end of the implant can recede. A portion of the abutment can be exposed and reveal a grayish color in the mouth of the patient.
Conventional dental implant restorations have other shortcomings as well. For example, much time and effort are needed to shape ceramic crowns to have a natural tooth-like configuration. Ceramic crowns currently on the market require the dental laboratory either to add or remove a substantial amount of material to the crowns to bring them to the approximate shape of a tooth. Material is added by baking porcelain to the ceramic surface. Many times, multiple layers of porcelain need to be added to achieve a natural shape and color. Each layer must be baked onto the crown before the next layer can be added. Multiple baking cycles can adversely affect the underlying ceramic substrate.
As another disadvantage, it is difficult to remove material from a hardened ceramic crown; and ceramics typically are very difficult to cut due to their hardness. Special water cooled diamond tools need to be used for such cuts. The stress associated with cutting the crown can also create microscopic fractures in the ceramic that weaken the material and make it susceptible to fatigue and ultimately failure.
Ceramic crowns are sold with various geometric shapes. One dental company sells crowns with a cone-shaped ceramic cylinder having an internal metal core. The ceramic cylinder tapers outwardly from the coronal end of the implant. The metal core is designed with a hexagon or other anti-rotational shape that is selected to match a mating feature on the implant body. Typically, the ceramic cylinder is large enough so excess material can be cut away to shape the crown. If the crown is not large enough, multiple layers of porcelain are baked to the outer surface to form the desired shape.
Other dental companies sell ceramic crowns with a generally cylindrical shape. The cylinder is sized slightly larger than the implant to facilitate cutting the crown to the geometry of a natural tooth. At the apical end of the crown, the ceramic tapers inwardly to the implant diameter. The cylinders include an anti-rotational feature to engage a coronal end of the implant.
Still, other companies manufacture ceramic caps that are cement-retained to a metal abutment. The ceramic cap has a cylindrical shape and must be cut to the shape and size of a natural tooth.
In light of prior ceramic prosthetic teeth and abutments, a ceramic crown that is initially shaped like a tooth would have many advantages over the prior art. The present invention provides such an advantage and other advantages taught herein.
The present invention is directed toward a prosthetic tooth that is manufactured to have a shape and size of a natural human tooth. The prosthetic tooth has an internal metallic core and an external ceramic crown. The core generally has a cylindrical configuration, an internal bore, and one end adapted to connect to a dental implant. The crown is formed from a ceramic that surrounds the outer surface of the core. Most importantly, the crown is manufactured to have an anatomical shape and size of a natural human tooth, such as incisors, molars, premolars, or canines. During a dental restoration, the clinician or laboratory chooses a correctly shaped and sized crown according to the tooth or teeth being restored.
A principal advantage of the present invention is the crown has a shape that closely resembles the shape of a natural tooth. This near net tooth shape of the crown will reduce the amount of work, time, and expense required to create a final dental prosthetic restoration. Further, the ceramic used to fabricate this crown is compatible with commercially available porcelains so that the gradients of shade and translucence of the natural tooth can be replicated. Also, the crown may be manufactured to have a size that is slightly smaller than the average natural tooth. This difference in size enables the crown to receive an additional layer of porcelain and then match the exact size of the natural tooth.
As another advantage, the prosthetic teeth of the present invention may be manufactured and sold as a kit. Each kit would include a plurality of prosthetic teeth having different sizes and shapes emulating different sizes and shapes of natural human teeth. A clinician could chose a prosthetic tooth to best match particular needs of a patient.
The present invention could also be manufactured and sold as a dental implant prosthetic system. This system would include both a dental implant and prosthetic tooth of the present invention.